Lithium ion battery

ABSTRACT

In a lithium ion battery, one or more chelating agents may be attached to a microporous polymer separator for placement between a negative electrode and a positive electrode or to a polymer binder material used to construct the negative electrode, the positive electrode, or both. The chelating agents may comprise, for example, at least one of a crown ether, a podand, a lariat ether, a calixarene, a calixcrown, or mixtures thereof. The chelating agents can help improve the useful life of the lithium ion battery by complexing with unwanted metal cations that may become present in the battery&#39;s electrolyte solution while, at the same time, not significantly interfering with the movement of lithium ions between the negative and positive electrodes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S. patentapplication Ser. No. 12/642,313, filed Dec. 18, 2009, which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

The technical field relates generally to secondary lithium ion batteriesand methods of making and using the same.

BACKGROUND

Secondary, or rechargeable, lithium ion batteries are well known andoften used in many stationary and portable devices such as thoseencountered in the consumer electronic, automobile, and aerospaceindustries. The lithium ion class of batteries have gained popularityfor various reasons including, but not limited to, a relatively highenergy density, a general nonappearance of any memory effect whencompared to other kinds of rechargeable batteries, a relatively lowinternal resistance, and a low self-discharge rate when not in use.

A lithium ion battery generally operates by reversibly passing lithiumions between a negative electrode (sometimes called the anode) and apositive electrode (sometimes called the cathode). The negative andpositive electrodes are situated on opposite sides of a microporouspolymer separator that is soaked with an electrolyte solution suitablefor conducting lithium ions. Each of the negative and positiveelectrodes is also accommodated by a current collector. The currentcollectors associated with the two electrodes are connected by aninterruptible external circuit that allows an electric current to passbetween the electrodes to electrically balance the related migration oflithium ions. The materials used to produce these various components ofa lithium ion battery are quite extensive. But in general, the negativeelectrode typically includes a lithium intercalation host material, thepositive electrode typically includes a lithium-based active materialthat can store lithium metal at a lower energy state than theintercalation host material of the negative electrode, and theelectrolyte solution typically contains a lithium salt dissolved in anon-aqueous solvent.

A lithium ion battery, or a plurality of lithium ion batteries that areconnected in series or in parallel, can be utilized to reversibly supplypower to an associated load device. A brief discussion of a single powercycle beginning with battery discharge can be insightful on this point.

To begin, during discharge, the negative electrode of a lithium ionbattery contains a high concentration of intercalated lithium while thepositive electrode is relatively depleted. The establishment of a closedexternal circuit between the negative and positive electrodes under suchcircumstances causes the extraction of intercalated lithium from thenegative anode. The extracted lithium is then split into lithium ionsand electrons. The lithium ions are carried through the micropores ofthe interjacent polymer separator from the negative electrode to thepositive electrode by the ionically conductive electrolyte solutionwhile, at the same time, the electrons are transmitted through theexternal circuit from the negative electrode to the positive electrode(with the help of the current collectors) to balance the overallelectrochemical cell. This flow of electrons through the externalcircuit can be harnessed and fed to a load device until the level ofintercalated lithium in the negative electrode falls below a workablelevel or the need for power ceases.

The lithium ion battery may be recharged after a partial or fulldischarge of its available capacity. To charge or re-power the lithiumion battery, an external power source is connected to the positive andthe negative electrodes to drive the reverse of battery dischargeelectrochemical reactions. That is, during charging, the external powersource extracts the intercalated lithium present in the positiveelectrode to produce lithium ions and electrons. The lithium ions arecarried back through the separator by the electrolyte solution and theelectrons are driven back through the external circuit, both towards thenegative electrode. The lithium ions and electrons are ultimatelyreunited at the negative electrode thus replenishing it withintercalated lithium for future battery discharge.

The ability of lithium ion batteries to undergo such repeated powercycling over their useful lifetimes makes them an attractive anddependable power source. But lithium ion battery technology isconstantly in need of innovative developments and contributions that canhelp to advance this and other related fields of technological art.

SUMMARY

One example of the disclosure is a microporous polymer separator, foruse in a lithium ion battery, to which one or more chelating agents maybe attached. The one or more chelating agents can complex with metalcations but do not strongly complex with lithium ions so that themovement of lithium ions across the microporous polymer separator duringoperation of the lithium ion battery is not substantially affected.

Another example of the disclosure is a lithium ion battery that maycomprise a negative electrode, a positive electrode, and a microporouspolymer separator situated between the negative electrode and thepositive electrode. The negative electrode may comprise a lithium hostmaterial and a polymer binder material. The positive electrode maycomprise a lithium-based active material and a polymer binder material.One or more chelating agents may be attached to at least one of themicroporous polymer separator, the binder material of the negativeelectrode, or the binder material of the positive electrode. The one ormore chelating agents can complex with metal cations but do not stronglycomplex with lithium ions so that the movement of lithium ions betweenthe negative and positive electrodes is not substantially affected.

Yet another example of the disclosure is a lithium ion battery that maycomprise a negative electrode, a positive electrode, an interruptibleexternal circuit that connects the negative electrode and the positiveelectrode, a microporous polymer separator to which one or morechelating agents are attached situated between the negative electrodeand the positive electrode, and an electrolyte solution capable ofconducting lithium ions soaked into the negative electrode, the positiveelectrode, and the microporous polymer separator. The microporouspolymer separator may comprise at least one of polyethylene orpolypropylene and have pendent groups or insoluble polymer bound groupsthat comprise the chelating agents. The chelating agents can complexwith metal cations that leach from the positive electrode. The chelatingagents, moreover, may comprise at least one of a crown ether, a podand,a lariat ether, a calixarene, a calixcrown, or a mixture of two or moreof these chelating agents.

Other examples of the disclosure will become apparent from the detaileddescription provided hereinafter. It should be understood that thedetailed description and specific examples, while disclosing examples ofthe disclosure, are intended for purposes of illustration only and arenot intended to limit the scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWING

Examples of the disclosure will become more fully understood from thedetailed description and the accompanying drawing, wherein:

FIG. 1 is a schematic and illustrative view of a lithium ion battery,during discharge, according to various examples of the disclosure. Theseparator is shown here to help illustrate the flow of ions between thenegative and positive electrodes and, as such, is not necessarily drawnto scale.

DETAILED DESCRIPTION

The following description of the example(s) is illustrative in natureand is not intended to limit the disclosure, its application, or uses.

A lithium ion battery can suffer cumulative capacity reductions andother detrimental effects, such as the reduction of solvent molecules,when destructive metal cations are introduced into its variouscomponents. To help address such an issue, an appropriate amount of oneor more chelating agents may be attached to the microporous polymerseparator situated between the negative and positive electrodes and/orto the polymer binder material used to construct the negative electrode,the positive electrode, or both. The chelating agents can be chosen toselectively complex with unwanted metal cations that may become presentin the electrolyte solution over the life of the battery. For example,in one example, the immobilization of certain metal cations that maydissolve into the electrolyte solution from the positive electrode(i.e., cations of manganese, cobalt, nickel, and/or iron) can helpprotect the lithium ion battery against negative electrode poisoning anda resultant reduction to its capacity and useful life. The chelatingagents thus operate as metal cation scavenger molecules that trap andimmobilize unwanted metal cations so as to prevent the migration ofthose metal cations through the electrolyte solution. But at the sametime, the chelating agents do not strongly complex with lithium ionsand, as such, will not adversely affect the movement of lithium ionsbetween the negative and positive electrodes to the point where anuncharacteristic reduction of the expected electrical current to besupplied by the battery occurs during discharge.

Referring now to FIG. 1, a schematic illustration of a secondary lithiumion battery 10 is shown that includes a negative electrode 12, apositive electrode 14, a microporous polymer separator 16 sandwichedbetween the two electrodes 12, 14, and an interruptible external circuit18 that connects the negative electrode 12 and the positive electrode14. Each of the negative electrode 12, the positive electrode 14, andthe microporous polymer separator 16 may be soaked in an electrolytesolution capable of conducting lithium ions. The microporous polymerseparator 16, which operates as both an electrical insulator and amechanical support, is sandwiched between the negative electrode 12 andthe positive electrode 14 to prevent physical contact between the twoelectrodes 12, 14 and the occurrence of a short circuit. The microporouspolymer separator 16, in addition to providing a physical barrierbetween the two electrodes 12, 14, may also provide a minimal resistanceto the internal passage of lithium ions (and related anions) to helpensure the lithium ion battery 10 functions properly. A negative-sidecurrent collector 12 a and a positive-side current collector 14 a may bepositioned at or near the negative electrode 12 and the positiveelectrode 14, respectively, to collect and move free electrons to andfrom the external circuit 18.

The lithium ion battery 10 may support a load device 22 that can beoperatively connected to the external circuit 18. The load device 22 maybe powered fully or partially by the electric current passing throughthe external circuit 18 when the lithium ion battery 10 is discharging.While the load device 22 may be any number of known electrically-powereddevices, a few specific examples of a power-consuming load deviceinclude an electric motor for a hybrid vehicle or an all-electricalvehicle, a laptop computer, a cellular phone, and a cordless power tool,to name but a few. The load device 22 may also, however, be apower-generating apparatus that charges the lithium ion battery 10 forpurposes of storing energy. For instance, the tendency of windmills andsolar panel displays to variably and/or intermittently generateelectricity often results in a need to store surplus energy for lateruse.

The lithium ion battery 10 can include a wide range of other componentsthat, while not depicted here, are nonetheless known to skilledartisans. For instance, the lithium ion battery 10 may include a casing,gaskets, terminal caps, and any other desirable components or materialsthat may be situated between or around the negative electrode 12, thepositive electrode 14, and/or the microporous polymer separator 16 forperformance-related or other practical purposes. Moreover, the size andshape of the lithium ion battery 10 may vary depending on the particularapplication for which it is designed. Battery-powered automobiles andhand-held consumer electronic devices, for example, are two instanceswhere the lithium ion battery 10 would most likely be designed todifferent size, capacity, and power-output specifications. The lithiumion battery 10 may also be serially connected, or connected in parallelwith other similar lithium ion batteries to produce a greater voltageoutput and power density if the load device 22 so requires.

The lithium ion battery 10 can generate a useful electric current duringbattery discharge by way of reversible electrochemical reactions thatoccur when the external circuit 18 is closed to connect the negativeelectrode 12 and the positive electrode 14 at a time when the negativeelectrode 12 contains a sufficiently higher relative quantity ofintercalated lithium. The chemical potential difference between thepositive electrode 14 and the negative electrode 12—approximately 3.7 to4.2 volts depending on the exact chemical make-up of the electrodes 12,14—drives electrons produced by the oxidation of intercalated lithium atthe negative electrode 12 through the external circuit 18 towards thepositive electrode 14. Lithium ions, which are also produced at thenegative electrode, are concurrently carried by the electrolyte solutionthrough the microporous polymer separator 16 and towards the positiveelectrode 14. The electrons flowing through the external circuit 18 andthe lithium ions migrating across the microporous polymer separator 16in the electrolyte solution eventually reconcile and form intercalatedlithium at the positive electrode 14. The electric current passingthrough the external circuit 18 can be harnessed and directed throughthe load device 22 until the intercalated lithium in the negativeelectrode 12 is depleted and the capacity of the lithium ion battery 10is diminished.

The lithium ion battery 10 can be charged or re-powered at any time byapplying an external power source to the lithium ion battery 10 toreverse the electrochemical reactions that occur during batterydischarge. The connection of an external power source to the lithium ionbattery 10 compels the otherwise non-spontaneous oxidation ofintercalated lithium at the positive electrode 14 to produce electronsand lithium ions. The electrons, which flow back towards the negativeelectrode 12 through the external circuit 18, and the lithium ions,which are carried by the electrolyte across the microporous polymerseparator 16 back towards the negative electrode 12, reunite at thenegative electrode 12 and replenish it with intercalated lithium forconsumption during the next battery discharge cycle. The external powersource that may be used to charge the lithium ion battery 10 may varydepending on the size, construction, and particular end-use of thelithium ion battery 10. Some suitable external power sources include,but are not limited to, an AC wall outlet and a motor vehiclealternator.

The negative electrode 12 may include any lithium host material that cansufficiently undergo lithium intercalation and deintercalation whilefunctioning as the negative terminal of the lithium ion battery 10. Thenegative electrode 12 may also include a polymer binder material tostructurally hold the lithium host material together. For example, inone example, the negative electrode 12 may be formed from graphiteintermingled in at least one of polyvinylidene fluoride (PVdF), anethylene propylene diene monomer (EPDM) rubber, or carboxymethylcellulose (CMC). Graphite is widely utilized to form the negativeelectrode because it exhibits favorable lithium intercalation anddeintercalation characteristics, is relatively non-reactive, and canstore lithium in quantities that produce a relatively high energydensity. Commercial forms of graphite that may be used to fabricate thenegative electrode 12 are available from, for example, Timcal Graphite &Carbon, headquartered in Bodio, Switzerland, Lonza Group, headquarteredin Basel, Switzerland, or Superior Graphite, headquartered in Chicago,USA. Other materials can also be used to form the negative electrodeincluding, for example, lithium titanate. The negative-side currentcollector 12 a may be formed from copper or any other appropriateelectrically conductive material known to skilled artisans.

The positive electrode 14 may be formed from any lithium-based activematerial that can sufficiently undergo lithium intercalation anddeintercalation while functioning as the positive terminal of thelithium ion battery 10. The positive electrode 14 may also include apolymer binder material to structurally hold the lithium-based activematerial together. One common class of known materials that can be usedto form the positive electrode 14 is layered lithium transitional metaloxides. For example, in various examples, the positive electrode 14 maycomprise at least one of spinel lithium manganese oxide (LiMn₂O₄),lithium cobalt oxide (LiCoO₂), a nickel-manganese-cobalt oxide[Li(Ni_(x)Mn_(y)CO_(z))O₂], or a lithium iron polyanion oxide such aslithium iron phosphate (LiFePO₄) or lithium iron fluorophosphate(Li₂FePO₄F) intermingled in at least one of polyvinylidene fluoride(PVdF), an ethylene propylene diene monomer (EPDM) rubber, orcarboxymethyl cellulose (CMC). Other lithium-based active materials mayalso be utilized besides those just mentioned, some examples of whichinclude lithium manganese phosphate; lithium vanadium phosphate; binarycombinations of lithium iron phosphate, lithium manganese phosphate, orlithium vanadium phosphate; a lithiated binary oxide of two elementschosen from manganese, nickel, and cobalt; or a lithiated ternary oxideof manganese, nickel, and cobalt. Other examples of alternativematerials include, but are not limited to, lithium nickel oxide(LiNiO₂), lithium aluminum manganese oxide (Li_(x)Al_(y)Mn_(1-y)O₂), andlithium vanadium oxide (LiV₂O₅), to name but a few. The positive-sidecurrent collector 14 a may be formed from aluminum or any otherappropriate electrically conductive material known to skilled artisans.

Any appropriate electrolyte solution that can conduct lithium ionsbetween the negative electrode 12 and the positive electrode 14 may beused in the lithium ion battery 10. In one example, the electrolytesolution may be a non-aqueous liquid electrolyte solution that includesa lithium salt dissolved in an organic solvent or a mixture of organicsolvents. Skilled artisans are aware of the many non-aqueous liquidelectrolyte solutions that may be employed in the lithium ion battery 10as well as how to manufacture or commercially acquire them. Anon-limiting list of lithium salts that may be dissolved in an organicsolvent to form the non-aqueous liquid electrolyte solution includeLiClO₄, LiAlCl₄, LiI, LiBr, LiSCN, LiBF₄, LiB(C₆H₅)₄ LiAsF₆, LiCF₃SO₃,LiN(CF₃SO₂)₂, LiPF₆, and mixtures thereof. These and other similarlithium salts may be dissolved in a variety of organic solvents such as,but not limited to, cyclic carbonates (ethylene carbonate, propylenecarbonate, butylene carbonate), acyclic carbonates (dimethyl carbonate,diethyl carbonate, ethylmethylcarbonate), aliphatic carboxylic esters(methyl formate, methyl acetate, methyl propionate), γ-lactones(γ-butyrolactone, γ-valerolactone), chain structure ethers(1,2-dimethoxyethane, 1-2-diethoxyethane, ethoxymethoxyethane), cyclicethers (tetrahydrofuran, 2-methyltetrahydrofuran), and mixtures thereof.

The microporous polymer separator 16 may comprise, in one example, apolyolefin. The polyolefin may be a homopolymer (derived from a singlemonomer constituent) or a heteropolymer (derived from more than onemonomer constituent), either linear or branched. If a heteropolymerderived from two monomer constituents is employed, the polyolefin mayassume any copolymer chain arrangement including those of a blockcopolymer or a random copolymer. The same holds true if the polyolefinis a heteropolymer derived from more than two monomer constituents. Inone example, the polyolefin may be polyethylene (PE), polypropylene(PP), or a blend of PE and PP.

In another example, the micorporous separator 16 may comprise a polymerchosen from polyethylene terephthalate (PET), polyvinylidene fluoride(PVdF), polyamides (Nylons), polyurethanes, polycarbonates, polyesters,polyetheretherketones (PEEK), polyethersulfones (PES), polyimides (PI),polyamide-imides, polyethers, polyoxymethylene (e.g., acetal),polybutylene terephthalate, polyethylenenaphthenate, polybutene,polyolefin copolymers, acrylonitrile-butadiene styrene copolymers (ABS),polystyrene copolymers, polymethylmethacrylate (PMMA), polyvinylchloride (PVC), polysiloxane polymers (such as polydimethylsiloxane(PDMS)), polybenzimidazole (PBI), polybenzoxazole (PBO), polyphenylenes(e.g., PARMAX™ (Mississippi Polymer Technologies, Inc., Bay Saint Louis,Mississippi)), polyarylene ether ketones, polyperfluorocyclobutanes,polytetrafluoroethylene (PTFE), polyvinylidene fluoride copolymers andterpolymers, polyvinylidene chloride, polyvinylfluoride, liquidcrystalline polymers (e.g., VECTAN™ (Hoechst AG, Germany) and ZENITE®(DuPont, Wilmington, Del.)), polyaramides, polyphenylene oxide, and/orcombinations thereof. It is believed that another example of a liquidcrystalline polymer that may be used as the polymer for the separator 16is poly-[p-hydroxybenzoic acid).

In yet another example, the microporous separator 16 may be chosen froma combination of the polyolefin (such as PE and/or PP) and one or moreof the polymers for the separator 16 listed above.

The microporous polymer separator 16 may be a single layer or amulti-layer laminate fabricated from either a dry or wet process. Forexample, in one example, a single layer of the polyolefin may constitutethe entirety of the microporous polymer separator 16.

In another example, a single layer of one or a combination of any of thepolymers from which the microporous polymer separator 16 may be formed(e.g, the polyolefin and/or one or more of the other polymers listedabove for the separator 16) may constitute the entirety of the separator16. As another example, however, multiple discrete layers of similar ordissimilar polyolefins and/or polymers for the separator 16 may beassembled into the microporous polymer separator 16. In one example, adiscrete layer of one or more of the polymers may be coated on adiscrete layer of the polyolefin for the separator 16. Further, thepolyolefin (and/or other polymer) layer, and any other optional polymerlayers, may further be included in the microporous polymer separator 16as a fibrous layer to help provide the microporous polymer separator 16with appropriate structural and porosity characteristics. Skilledartisans will undoubtedly know and understand the many availablepolymers and commercial products from which the microporous polymerseparator 16 may be fabricated, as well as the many manufacturingmethods that may be employed to produce the microporous polymerseparator 16. A more complete discussion of single and multi-layerlithium ion battery separators, and the dry and wet processes that maybe used to make them, can be found in P. Arora and Z. Zhang, “BatterySeparators,” Chem. Rev., 104, 4424-4427 (2004).

The chelating agents, which may be attached to the microporous polymerseparator 16 and/or the polymer binders in at least one of the negativeelectrode 12 or the positive electrodes 14, may be any of a variety ofmolecules that can complex with unwanted metal cations to form stableand neutral compounds while, at the same time, not adversely affectingthe flow of lithium ions between the negative and positive electrodes12, 14. The particular chelating agent or agents may, in some instances,be chosen to selectively complex with certain metal cations that areknown or expected to be present in the electrolyte solution at somepoint during operational lifetime of the lithium ion battery 10. Forexample, spinel lithium manganese oxide (LiMn₂O₄) that may be present inthe positive electrode 14 may leach Mn²⁺ cations into the electrolytesolution during normal operation of the lithium ion battery 10. Thesemobile Mn²⁺ cations, in turn, can migrate through the electrolytesolution and across the microporous polymer separator 16 until theyeventually reach the negative electrode 12. Moreover, if the negativeelectrode 12 is formed from graphite, the Mn²⁺ cations that reach thenegative electrode 12 tend to undergo a reduction reaction and depositon the graphite surface since the standard redox potential of Mn/Mn(II)is much higher than that of lithium intercalation into graphite. Thedeposition of manganese onto graphite in the negative electrode 12catalyzes the reduction of solvent molecules at the contaminatedinterface of the negative electrode 12 and the electrolyte solutioncausing the evolution of gases. The poisoned portion of the negativeelectrode 12 is essentially deactivated and no longer able to facilitatethe reversible gain and loss of intercalated lithium. Similarly, thedissolution of cobalt cations and iron cations from lithium cobalt oxide(LiCoO₂) and lithium iron phosphate (LiFePO₄), respectively, that may bepresent in the positive electrode 14 can also cause capacity losses inthe lithium ion battery 10 by the same or related mechanism. Theleaching of cobalt cations may occur, in one instance, because of anancillary chemical reaction with various adhesives normally used in thepackaging of the lithium ion battery 10. The leaching of iron cationsmay occur, in one instance, because of the presence of hydrofluoric acidthat may be produced through the ingress and egress of water into theelectrolyte solution. Furthermore, nickel cations may come from cathodematerials containing ternary mixed Ni-Mn-Co oxides.

But regardless of the lithium-based active material(s) used in thepositive electrode 14, the leaching rate of metal cations into theelectrolyte solution may vary. The leaching rate of metal cations frompositive electrode 14 may be relatively slow and require several yearsfor the electrolyte solution to accumulate a concentration of associatedmetal cations measurable in parts per million (ppm). The leaching rateof metal cations from the positive electrode 14 may also, on the otherhand, be relatively fast in that the concentration of associated metalcations in the electrolyte solution increases by about 0.1 weightpercent per battery power cycle. The leaching of any amount of metalcations from the positive electrode 14, whether slow or fast, cannevertheless poison large areas of the graphite in the negativeelectrode 12 and ultimately cause a noticeable and performance-affectingreduction in capacity of the lithium ion battery 10. An amount ofchelating agents effective to sequester the cumulative dissolution ofmetal cations into the electrolyte solution during the operationallifetime of the lithium ion battery 10 may therefore be attached to themicroporous polymer separator 16 and/or the polymer binding materials inat least one of the negative or positive electrodes 12, 14. The exactamount of chelating agents employed, which may vary considerably, isgenerally predicated on the chemistry of the lithium ion battery 10, thecompositional make-up of the negative and positive electrodes 12, 14,and the expected or observed rate at which unwanted metal cations areintroduced into the electrolyte solution during operation of the lithiumion battery.

The chelating agents may comprise, for example, at least one of a crownether, a podand, a lariat ether, a calixarene, a calixcrown, or mixturesthereof. These chelating agents are useful because they will notstrongly complex with the relatively small lithium ions moving betweenthe negative and positive electrodes 12, 14 because of their size andspatial constructions. Skilled artisans will generally know andunderstand, or be able identify, the many molecular compounds that mayconstitute these classes of chelating agents. A generalized descriptionof these chelating agents is nonetheless provided here for convenience.

A crown ether is a macrocyclic polyether in which the polyether ringincludes oxygen donor atoms that can complex with a metal cation. Someor all of the oxygen donor atoms in the polyether ring may be exchangedfor nitrogen atoms, a class of crown ethers known as azacrowns, orsulfur atoms, a class of crown ethers known as thiacrowns. The crownether may be monocyclic, in which the crown ether forms a somewhattwo-dimensional ring for complexing with a metal cation, or polycyclic,in which the crown ether forms a more three-dimensional cage forcomplexing with a metal cation. One example of a polycyclic crown etheris a cryptand. The crown ether may also be substituted at any locationalong its polyether ring by any of a variety of groups known to thoseskilled in the art. For instance, the crown ether may bethia-substituted (i.e., substituted with S atoms rather than O atoms) oraza-substituted (i.e., substituted with N atoms rather than O atoms). Apodand is an acyclic polyether ligand that includes donor-group-bearingarms that can complex with a metal cation. A lariat ether is a crownether that includes a donor-group-bearing side-arm that providesadditional metal cation binding sites beyond those present on thepolyether ring. A calixarene is a metacyclophane of methylene-bridgedphenol units, and is generally found in one of a cone, partial cone,1,2-alternate, or 1,3-alternate conformation. A calixcrown is acalixarene that includes a polyether ring that links two phenolicoxygens of the calixarene framework. The indifference these chelatingagents show towards complexing with lithium ions is likely ascribed totheir relatively large polyether ring or cage structures and/or thespatial orientation of their functional donor-group-bearing arms whencompared to the relatively small size of lithium ions. Analogs andstructurally related molecules of the chelating agents just mentionedmay also be employed.

A nonexhaustive list of crown ethers that can complex with metal cationswhich may, for example, leach into the electrolyte solution from thepositive electrode 14 (such as cations of manganese, cobalt, and iron)includes (1) 15-crown-5, (2) dibenzo-15-crown-5, (3) 18-crown-6, (4)benzo-18-crown-6, (5) dibenzo-18-crown-6, (6) dibenzo-21-crown-7, (7)dicyclohexano-18-crown-6, (8) dicyclohexano-24-crown-8, (9)poly(dibenzo-18-crown-6), (10) 1,4,7,10,13,16-hexathia-18-crown-6, (11)1,4,7,10,13,16-hexaaza-18-crown-6, (12) 1-aza-18-crown-6, (13)1,10-diaza-18-crown-6, (14) N,N′-dibenzyl-4,13-diaza-18-crown-6, and(15) 4,7,13,16,21,24-hexaoxa-1,10-diazabycyclo[9.8.8]hexacosane, thestructures of which are shown below. The hydrogen atoms in structures11-13 are assumed.

Some more examples of crown ethers, including thiacrowns and azacrowns,that may be attached to the microporous polymer separator 16 can befound in W. Walkowiak and C. A. Kozlowski, “Macrocycle Carriers forSeparation of Metal Ions in Liquid Membrane Processes—A Review,”Desalination 240, Table 1 on pg. 189 (compounds I-15 that are notalready mentioned above) (2009); R. L Bruening, R. M. Izatt, and J. S.Bradshaw, “Understanding Cation-Macrocycle Binding Selectivity inSingle-Solvent Extractions, and Liquid Membrane Systems by QuantifyingThermodynamic Interactions, FIG. 1 on pg. 112 in “Cation Binding byMacrocycles,” Y. Inoue and G. W. Gokel (editors), Chapter 2, 1990,Marcel Dekker Inc., New York and Basel; J. L. Tonor, “Modern Aspects ofHost-Guest Chemistry Molecular Modeling and Conformationally RestrictedHosts,” FIG. 2 on pg. 82 in “Crown Ethers and Analogs,” S. Patai and Z.Rappaport (editors), Chapter 3, 1989, John Wiley and Sons, New York; F.Vogtle and E. Weber, “Crown-ether-complexes and Selectivity,” FIGS. 1,2, and 3 on pg. 209, 210, and 211, respectively, in “Crown Ethers andAnalogs,” S. Patai and Z. Rappaport (editors), Chapter 4, 1989, JohnWiley and Sons, New York, the above-identifed portions of each referencebeing hereby incorporated by reference.

A nonexhaustive list of podands that can complex with metal cationswhich may, for example, leach into the electrolyte solution from thepositive electrode 14 can be found in W. Walkowiak and C. A. Kozlowski,“Macrocycle Carriers for Separation of Metal Ions in Liquid MembraneProcesses—A Review,” Desalination 240, Table 2 on pg. 190 (compounds 32aand 32b) (2009); A. Shahrisa and A. Banaei, “Chemistry of Pyrones, Part3: New Podands of 4H-Pyran-4-ones, 5 Molecules,” FIGS. 1 and 3 on pg.201 (2000); and F. Vögtle and E. Weber, “Crown-ether-complexes andSelectivity,” FIGS. 4, 5, 6, and 7 on pg. 212, 213, 214, and 215,respectively, in “Crown Ethers and Analogs,” S. Patai and Z. Rappaport(editors), Chapter 4, 1989, John Wiley and Sons, New York; and CrownEthers and Analogs, edited by Patai and Rappoport, (1989), theabove-identified portions of each reference being hereby incorporated byreference.

A nonexhaustive list of lariat ethers that can complex with metalcations which may, for example, leach into the electrolyte solution fromthe positive electrode 14 can be found in W. Walkowiak and C. A.Kozlowski, “Macrocycle Carriers for Separation of Metal Ions in LiquidMembrane Processes—A Review,” Desalination 240, Table 1 on pg. 189(compounds 16-18) (2009); and E. Weber, “New Developments in Crown EtherChemistry: Lariats, Spherands, and Second-Sphere Complexes,” FIGS. 2, 4,and 6 on pg. 307, 309, and 315, respectively, in “Crown Ethers andAnalogs,” S. Patai and Z. Rappaport (editors), Chapter 5, 1989, JohnWiley and Sons, New York, the above-identified portions of eachreference being hereby incorporated by reference.

A nonexhaustive list of calixarenes that can complex with metal cationswhich may, for example, leach into the electrolyte solution from thepositive electrode 14 can be found in W. Walkowiak and C. A. Kozlowski,“Macrocycle Carriers for Separation of Metal Ions in Liquid MembraneProcesses—A Review,” Desalination 240, Table 2 on pg. 190 (compounds22-23) (2009); and J. L. Atwood, “Cation Complexation by Calixarenes,”FIGS. 6 and 7 on pg. 587 (the ester functionalized calixarenes) in“Cation Binding by Macrocycles,” Y. Inoue and G. W. Gokel (editors),Chapter 15, 1990, Marcel Dekker Inc., New York and Basel, theabove-identified portions of each reference being hereby incorporated byreference.

A nonexhaustive list of calixcrowns that can complex with metal cationswhich may, for example, leach into the electrolyte solution from thepositive electrode 14 can be found in W. Walkowiak and C. A. Kozlowski,“Macrocycle Carriers for Separation of Metal Ions in Liquid MembraneProcesses—A Review,” Desalination 240, Table 2 on pg. 190 (compounds24-27, compound 28 with ester functionality, and compounds 30-31)(2009), the above-identified portions of each reference being herebyincorporated by reference.

There are, of course, many other crown ethers, podands, lariat ethers,calixarenes, calixcrowns, and related chelating agents that are known toskilled artisans, but are not specifically mentioned here, that can beattached to the microporous polymer separator 16 to sequester andimmobilize unwanted metal cations that may be introduced into theelectrolyte solution of the lithium ion battery 10.

The chelating agents may be attached to the microporous polymerseparator 16 and the polymer binders of the negative and positiveelectrodes 12, 14 by any known method. For example, in one example, apendant group that comprises the chelating agent may be grafted onto thepolyolefin used to make the microporous polymer separator 16. Thechelating agents may be attached uniformly throughout polyolefin or theymay be locally attached at predetermined locations. A greaterconcentration of the chelating agents may, for example, be provided onthe side of the microporous polymer separator 16 that faces the positiveelectrode 14. Such a build-up of chelating agents on thepositive-electrode-side of the microporous polymer separator 16 can helpfacilitate the earliest possible sequestering of any destructive metalcations that leach into the electrolyte solution from the positiveelectrode 14. Pendent groups that comprise the chelating agents may alsobe similarly grafted onto the other polymers in the microporous polymerseparator 16, if present. In another example, an insoluble polymer boundgroup that comprises the chelating agent may be entangled in, andoptionally crosslinked to, the polymer matrix of the microporous polymerseparator 16 and/or the polymer binder materials of at least one of thenegative or positive electrodes 12, 14. The polymer bound group may bepolyolefin, or some other polymer with similar properties, that includesa pendent group that comprises the chelating agent.

A poly(1-olefin) may be prepared, for instance, from the Ziegler-Nattapolymerization of functionally substituted polyolefins or by metathesispolymerization. The resultant poly(1-olefins) may then be functionalizedwith the chelating agents. The same chelating agent substitutedpolyolefins may also be prepared by the polymerization of α,ω-olefins orpre-formed prepolymers that have been substituted with pendant chelatingagent groups. Polyolefin heteropolymers, such as polyundecylenol, may beformed by either method and generally involve the controlled feed ofsimilarly sized (i.e., number of carbons) olefin monomers or prepolymersduring polymerization. The chelating agent substituted polyolefins, onceprepared, may then be incorporated into the microporous polymerseparator 16. In one example, the chelating agent substitutedpolyolefins may be manufactured into a fairly rigid fibrous polyolefinlayer that may constitute all or part of the microporous polymerseparator 16. In another example, however, the chelating agentsubstituted polyolefins may be insolubly bound within the polymer matrixof a separate fibrous polymer layer that is intended for use as all orpart of the microporous polymer separator 16, or they may be insolublybound within the polymer matrix of a polymer binder materials that isintended to be included in at least one of the negative or positiveelectrodes 12, 14.

The following examples are provided to help illustrate how a chelatingagent substituted polyolefin may be prepared, and how such polyolefinsmay be incorporated into the microporous polymer separator 16 and/or thepolymer binder materials of at least one of the negative or positiveelectrodes 12, 14. Example 1 demonstrates the preparation of apolyolefin that includes pendent crown ether groups in which afunctionally substituted polyolefin was polymerized and then substitutedwith crown ether groups. Example 2 demonstrates the preparation of apolyolefin that includes pendent crown ether groups in which olefinswere substituted with crown ether groups and then polymerized. Example 3demonstrates the manufacture of a microporous polymer separator from thepolyolefins of either Example 1 or Example 2. The microporous polymerseparator manufactured in Example 3 includes a polyolefin layer havingpendent crown ether groups. Example 4 demonstrates the manufacture of amicroporous polymer separator or a negative electrode. In that Example,crown ether substituted polyolefins are insolubly bound within thepolymer matrix of a commercially available polyolefin battery separatoror a commercially available polymer binder material. Those materials maythen be incorporated into a microporous polymer separator or a negativeelectrode, respectively.

Example 1

In this example, a polyolefin with pendent 18-crown-6 groups (crownether chelating agent) is prepared by the Zeigler-Natta polymerizationof a halogenated polyolefin that is subsequently substituted withfunctionalized crown ether groups. The halogenated polyolefins may beformed by the direct polymerization of halo-functionalized monomers orthe chemical modification of pre-formed prepolymers. To accomplish this,at least one α,ω-olefin such as 11-undecylenyl bromide (or iodide),6-bromo-1-hexene, or 5-bromo-1-pentene may be polymerized with at leastone 1-olefin such as ethane, propene, or 1-butene at a prefixedα,ω-olefin:1-olefin weight ratio of, for example, 1:9, 2:8, 3:7, or 5:5in toluene. A catalyst, such as TiCl₃.AA/Et₂AlCl, may be used to makeisotactic poly-α-olefins that form α-helix structures and polymerize theco-substituted α-olefins. This polymerization reaction proceeds mostefficiently when bulky monomer or prepolymer functionalized units thatdo not coordinate with the catalyst are used [e.g. CH₂═CH—(CH₂)_(y)—X].Large halo groups (X) may also enhance the polymerization reaction(i.e., I>Br>Cl). The resultant polymers, which are soluble in hottoluene, can form carboxylic acid and alcohol functional groups byprotection with, for example, trimethylsilyl-groups [—Si(CH₃)₃], whichare readily removed on work-up with aqueous acids. Nucleophilicdisplacement of the halide ion with 2-hydroxymethyl-18-crown-6,hydroxymethyl-benzo-18-crown-6, or 2-aminobenzo-18-crown-6 in thepresence of sodium hydride, potassium carbonate and/or lutidine may thenbe achieved to attach pendent groups containing 18-crown-6 to thepolyolefins. Moroever, at high concentrations of crown ether substituentgroups, the polyolefins become less crystalline and may therefore bereinforced with 1,6-hexadience as a co-reactant to cross-link thepolyolefins. The overall reaction in which pendent 18-crown-6 groups aregrafted onto a polyolefin is shown below, where X may be I or Br, and Ymay be 2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo.

Example 2

In this example, a polyolefin with pendent 18-crown-6 groups (crownether chelating agent) is prepared by polymerizing α,ω-olefins orpre-formed prepolymers that have first been substituted with pendantcrown ether groups. Crown ether substituted α,ω-olefins may be preparedby reacting at least one of 11-undecylenyl bromide (or iodide),6-bromo-1-hexene, or 5-bromo-1-pentene with at least one ofhydroxymethyl-18-crown-6 or hydroxymethyl-benzo-18-crown-6 inN,N-dimethylacetamide. Alcohol functional groups may be formed on theα,ω-olefins by protection with, for example, trimethylsilyl-groups[—Si(CH₃)₃], which are readily removed on work-up with aqueous acids.Nucleophilic displacement of the halide ion with2-hydroxymethyl-18-crown-6 or hydroxymethyl-benzo-18-crown-6 in thepresence of potassium carbonate and/or lutidine may then proceed untilthe bromo (or iodo) groups on the am-olefins are replaced with18-crown-6 groups. The crown ether substituted α,ω-olefins are thenpolymerized with at least one 1-olefin such as ethane, propene, or1-butene at a pre-fixed α,ω-olefin:1-olefin weight ratio of, forexample, 1:9, 2:8, 3:7, or 5:5 in toluene. A catalyst, such asTiCl₃.AA/Et₂AlCl, may be used to make isotactic poly-α-olefins that formα-helix structures and polymerize the ω-substituted α-olefins. Moroever,at high concentrations of crown ether substituent groups, thepolyolefins become less crystalline and may therefore be reinforced with1,6-hexadience as a co-reactant to cross-link the polyolefin. Theoverall reaction in which pendent 18-crown-6 groups are grafted onto apolyolefin is shown below, where X may be I or Br, and Y may be2-hydroxymethyl, hydroxymethyl-benzo, or 2-aminobenzo.

In a typical reaction, 6-bromo-1-hexene is allowed to react with a onemolar ratio of hydroxymethyl-benzo-18-crown-6 in N,N-dimethylacetamidefor 1 week at 50° C. under argon in a sealed vessel in the presence ofexcess sodium hydride, potassium carbonate and a molecular equivalent oflutidine. The reaction mixture is filtered and the solvent and lutidineare then removed under vacuum and 1-hexyl-6-benzo-18-crown-6 is purifiedon silica gel by column chromatography eluting with tetrahydrofuran,methylene chloride, or ethyl acetate and hexanes. After removal of thesolvent, the residue is dissolved in 10 wt. % toluene, 1 wt. %1,6-hexadiene, and with 89 wt. % 1-butene bubbled into a glass beveragebottle with a rubber septum that is situated in an ice bath. Thereactants in toluene are double-needle, dropwise transferred intoanother beverage bottle with a rubber septum under argon, situated in anice bath, and containing a magnetic stir bar, toluene, TiCl₃.AA, 25 wt.% diethylaluminum chloride in toluene, and optionally a 1.1 molarsolution of diethyl zinc, all of which are added to methanol using aWaring blender to fibrillate the precipitated crown ether substitutedpolyolefin as a fibrous pulp.

OTHER EXAMPLES

A more complete discussion of various techniques that can be used tograft crown ethers onto polymer backbones can be found in J. Smid, PureAppl. Chem., 48, 343 (1976), J. Smid, Makrom. Chem. Supp., 5, 203(1981), J. Smid, Pure Appl. Chem., 54, 2129 (1982), and U. Tunca and Y.Yagci, “Crown Ether Containing Polymers,” Prog. Polym. Sci., 19, 233-286(1994). Another method of making poly(olefins) with pendent crown ethersis to prepare poly(vinyl benzyl alcohol) containing polymers, asdiscussed in U.S. Pat. No. 6,200,716 to Fuller, and then react thosepolymers with chloromethyl-benzo-18-crown-6 in N,N-dimethylacetamide.Still another method involves preparing olefinic polymers withundecylenyl alcohol groups and allowing those polymers to react withlithium hydride or sodium hydride in tetrahydrofuran in the presence ofchloromethyl-benzo-18-crown-6.

Example 3

The crown ether substituted polyolefins prepared by the method of eitherExample 1 or Example 2 may be added to a non-solvent such as methanol toform insoluble flocculated fibrous materials (flocs). The crown ethersubstituted polyolefins may, alternatively, be quenched with methanol,washed with water, and then stripped of toluene under reduced pressure.The polyolefins may then be fibrillated in a non-solvent such as waterusing a Waring blender. Next, the fibrillated polyolefins may be pouredonto and laid down on a porous screen. The wet pulp polyolefin materialmay then be pressed to remove any residual non-solvent to form a fibrousmat, and subsequently hot pressed below the melting point of thepolyolefin to form a fairly rigid crown ether substituted fibrouspolyolefin material layer. The resultant polymer layer may then beutilized in a lithium ion battery as either a single layer microporouspolymer separator or as part of a mult-layer microporous polymerseparator.

Example 4

The crown ether substituted olefins (vinyl benzo-18-crown-6) prepared bythe method described by J. Smid (see OTHER EXAMPLES above), or purchasedfrom Aldrich of Milwaukee, Wis., may be dissolved in a toluene orbenzene solution that optionally, but preferably, includes across-linking agent such as divinylbenzene with azobisisobutyronitrile(0.1 wt. % monomer mass). A commercial polyolefin lithium ion batteryseparator or a commercially available binder material may be dipped intothe solution with subsequent heating under nitrogen between 60° C. and80° C. so that polymerization of the crown ether substituted olefins canoccur in the presence of the separator or polymer binder material.Commercial polyolefin battery separators, either single ormulti-layered, are available from Asahi Kasei, headquartered in Tokyo,Japan, Celgard LLC, headquartered in Charlotte, N.C., Ube Industries,headquartered in Tokyo, Japan, and Mitsui Chemicals, headquartered inTokyo, Japan, to name but a few manufacturers. The dissolved crown ethersubstituted polyolefins, at this point, become snagged in the polymermatrix of the commercial battery separator or the commercially availablepolymer binder material. Later, when the commercial battery separator orthe commercially available polymer binder material is removed from thesolution and air dried, the entrapped crown ether substitutedpolyolefins become insoluble polymer bound polyolefin particles. Thepresence of a cross-linker can enhance the entanglement of the crownether substituted polyolefins contained in the commercial batteryseparator or the commercially available polymer binder material bypromoting the formation of stronger polymer-polymer bonds between thepolymer bound crown ether substituted polyolefins and between thepolymer bound crown ether substituted polyolefins and the commercialbattery separator/commercial polymer binder materials.

It is to be understood that, as used herein, the singular forms of thearticles “a,” “an,” and “the” include plural references unless thecontent clearly indicates otherwise.

While several examples have been described in detail, it will beapparent to those skilled in the art that the disclosed examples may bemodified. Therefore, the foregoing description is to be considerednon-limiting.

1. A microporous polymer separator for use in a lithium ion battery,comprising: one or more chelating agents attached to the microporouspolymer separator, the one or more chelating agents configured tocomplex with metal cations in a manner sufficient to not affect movementof lithium ions across the microporous polymer separator duringoperation of the lithium ion battery; wherein the microporous polymerseparator comprises a polymer chosen from polyethylene terephthalates,polyvinylidene fluorides, polyamides, polyurethanes, polycarbonates,polyesters, polyetheretherketones, polyethersulfones, polyimides,polyamide-imides, polyethers, polyoxymethylenes, polybutyleneterephthalates, polyethylenenaphthenates, polybutenes, polyolefins,polyolefin copolymers, acrylonitrile-butadiene styrene copolymers,polystyrene copolymers, polymethylmethacrylates, polyvinyl chlorides,polysiloxane polymers, polybenzimidazoles, polybenzoxazoles,polyphenylenes, polyarylene ether ketones, polyperfluorocyclobutanes,polytetrafluoroethylenes, polyvinylidene fluoride copolymers,polyvinylidene fluoride terpolymers, polyvinylidene chlorides,polyvinylfluorides, liquid crystalline polymers, polyaramides,polyphenylene oxides, or combinations thereof.
 2. The microporouspolymer separator as defined in claim 1 wherein the one or morechelating agents comprise at least one of a crown ether, a podand, alariat ether, a calixarene, or a calixcrown.
 3. The microporous polymerseparator as defined in claim 1 wherein the metal cations include anelement chosen from at least one of Mn, Co, Ni, or Fe.
 4. Themicroporous polymer separator as defined in claim 1 wherein the polymercomprises pendent groups comprising the one or more chelating agents. 5.The microporous polymer separator as defined in claim 1 wherein thepolyolefin is chosen from polyethylene, polypropylene, or combinationsthereof.
 6. The microporous polymer separator as defined in claim 1wherein the polymer is provided as a layer that forms the entirety ofthe microporous polymer separator.
 7. The microporous polymer separatoras defined in claim 1 wherein the polymer is provided as a layer thatforms part of the microporous polymer separator.
 8. A microporouspolymer separator for use in a lithium ion battery, comprising: one ormore chelating agents attached to the microporous polymer separator, theone or more chelating agents to complex with metal cations in a mannersufficient to not affect movement of lithium ions across the microporouspolymer separator during operation of the lithium ion battery; whereinthe microporous polymer separator, comprises: a discrete layer of apolyolefin; and an other discrete layer of a polymer, the polymer beingchosen from polyethylene terephthalates, polyvinylidene fluorides,polyamides, polyurethanes, polycarbonates, polyesters,polyetheretherketones, polyethersulfones, polyimides, polyamide-imides,polyethers, polyoxymethylenes, polybutylene terephthalates,polyethylenenaphthenates, polybutenes, polyolefins, polyolefincopolymers, acrylonitrile-butadiene styrene copolymers, polystyrenecopolymers, polymethylmethacrylates, polyvinyl chlorides, polysiloxanepolymers, polybenzimidazoles, polybenzoxazoles, polyphenylenes,polyarylene ether ketones, polyperfluorocyclobutanes,polytetrafluoroethylenes, polyvinylidene fluoride copolymers,polyvinylidene fluoride terpolymers, polyvinylidene chlorides,polyvinylfluorides, liquid crystalline polymers, polyaramides,polyphenylene oxides, or combinations thereof.
 9. The microporouspolymer separator as defined in claim 8 wherein the one or morechelating agents comprise at least one of a crown ether, a podand, alariat ether, a calixarene, or a calixcrown.
 10. The microporous polymerseparator as defined in claim 8 wherein at least one of the polyolefinor the polymer includes pendent groups comprising the one or morechelating agents.
 11. The microporous polymer separator as defined inclaim 8 wherein the polyolefin is chosen from polypropylene,polyethylene, or combinations thereof.
 12. A lithium ion battery,comprising: a negative electrode comprising a lithium host material anda polymer binder material; a positive electrode comprising alithium-based active material and a polymer binder material; and amicroporous polymer separator situated between the negative electrodeand the positive electrode, the microporous polymer separator comprisinga polymer chosen from polyethylene terephthalates, polyvinylidenefluorides, polyamides, polyurethanes, polycarbonates, polyesters,polyetheretherketones, polyethersulfones, polyimides, polyamide-imides,polyethers, polyoxymethylenes, polybutylene terephthalates,polyethylenenaphthenates, polybutenes, polyolefins, polyolefincopolymers, acrylonitrile-butadiene styrene copolymers, polystyrenecopolymers, polymethylmethacrylates, polyvinyl chlorides, polysiloxanepolymers, polybenzimidazoles, polybenzoxazoles, polyphenylenes,polyarylene ether ketones, polyperfluorocyclobutanes,polytetrafluoroethylenes, polyvinylidene fluoride copolymers,polyvinylidene fluoride terpolymers, polyvinylidene chlorides,polyvinylfluorides, liquid crystalline polymers, polyaramides,polyphenylene oxides, or combinations thereof; wherein one or morechelating agents are attached to at least one of the polymer of themicroporous polymer separator, the binder material of the negativeelectrode, or the binder material of the positive electrode, and whereinthe one or more chelating agents complex with metal cations in a mannersufficient to not affect movement of lithium ions across the microporouspolymer separator during operation of the lithium ion battery.
 13. Thelithium ion battery as defined in claim 12 wherein the negativeelectrode further comprises graphite, and wherein the positive electrodefurther includes: spinel lithium manganese oxide; lithium cobalt oxide;lithium iron phosphate; lithium manganese phosphate; lithium vanadiumphosphate; binary combinations of lithium iron phosphate, lithiummanganese phosphate, or lithium vanadium phosphate; a lithiated binaryoxide of two elements chosen from manganese, nickel, and cobalt; or alithiated ternary oxide of manganese, nickel, and cobalt.
 14. Thelithium ion battery as defined in claim 12 wherein the polymer bindermaterial of the negative electrode and the polymer binder material ofthe positive electrode comprise at least one of polyvinylidene fluoride,an ethylene polypropylene diene monomer rubber, or carboxymethylcellulose.
 15. The lithium ion battery as defined in claim 12 whereinthe chelating agents comprise at least one of a crown ether, a podand, alariat ether, a calixarene, or a calixcrown.
 16. The lithium ion batteryas defined in claim 12, further comprising: an interruptible externalcircuit that connects the negative electrode and the positive electrodeand transmits an electric current therebetween; and an electrolytesolution that is capable of conducting lithium ions soaked into thenegative electrode, the positive electrode, and the microporous polymerseparator.
 17. The lithium ion battery as defined in claim 12 whereinthe polymer of the microporous polymer separator comprises pendentgroups that comprise the one or more chelating agents.